Re: json_populate_recordset and nested object, how to solve?

[Raphael Bauduin <rblists@xxxxxxxxx>]

MatheusOl helped me solve this on IRC, sending it here in case it helps someone looking at the archives of the mailing list.

Here is a test case

create table t(id SERIAL, event json);

insert into t(event) VALUES ('{"type":"show", "products": [ { "id" : 1, "name" : "p1"}] }'::json);

insert into t(event) VALUES ('{"type":"show", "products": [ { "id" : 1, "name" : "p1" , "stock" : [ {"XL" : 1}] }] }'::json);

create type product as (id int, name text );


select rs.* from (select * from t where id=1) e   CROSS JOIN LATERAL json_populate_recordset(null::product, e.event->'products') rs;
--works

select rs.* from (select * from t where id=2) e   CROSS JOIN LATERAL json_populate_recordset(null::product, e.event->'products') rs;
-- error:
ERROR:  cannot call json_populate_recordset on a nested object

and the simple solution I was looking for:

 SELECT (p->>'id')::int AS id, p->>'name' AS name FROM (SELECT json_array_elements(event->'products') AS p FROM t) t1;

Raph

On Fri, Apr 4, 2014 at 10:25 AM, Raphael Bauduin <rblists@xxxxxxxxx> wrote:

Hi,

here is an example of a problem I encounter with json_populate_recordset because it does not support nested object. Actually, I would prefer that it ignores nested object rather than raise an error, as it fails on a key I don't even want to use!

Here's the query:

select e.timestamp::date, e.user_id, rs.similarity from
  (select * from events where type='suggestion' and timestamp<'2014-04-04' and timestamp>'2014-04-03') e
   CROSS JOIN LATERAL
  json_populate_recordset(null::suggestion, event->'products') rs
order by e.user_id;


event->'products' is an array of json objects, one of this keys (stock) being an array of json objects. I can absolutely ignore that key in this query, but I don't see how. The suggestion type does not have a stock key, so it would be absent of the result anyway.

So, how would you get event->'products' without the stock keys, just to be able to call json_populate_recordset?

Thanks.

Raph

PS: this might be seen as a followup to a previous mail thread: http://www.postgresql.org/message-id/CAONrwUGMQthsut_F8X4CBGQDuKa5=A+AtmxSXb2FdOXh5PD3Qg@xxxxxxxxxxxxxx
but I don't see how to apply that suggestion here.

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